A motor vehicle is typically provided with an air inlet comprising one or more air inlet openings. An air inlet is commonly used to cool the motor of the motor vehicle during operation. Air inlets are usually located at a front of the motor vehicle in front of the motor. Usually a motor can be cooled by means of a coolant, for example, water or oil. This coolant is cooled with air in a heat exchanger, for instance, in a radiator. The air flowing through the air inlet may be guided wholly or partly to the radiator of the motor compartment of the motor of the motor vehicle to cool the motor indirectly via the coolant. It is known to make an air inlet of a motor compartment of adjustable design, allowing the air inlet to be adjusted between an open position and a closed position.
In the closed position of the air inlet the air resistance of the vehicle is lowered, which is beneficial to the fuel consumption of the motor. Moreover, where the efficiency of the motor, fuel consumption and CO2 emission are concerned, a motor of a motor vehicle has an optimum operating temperature, which is typically higher than the ambient temperature. A closed air inlet when the motor is cold is then once again beneficial to fuel consumption. Also, during driving with an open air inlet, the temperature of the motor can fall below the optimum operating temperature, so that fuel consumption may increase. Also at an operating temperature above the optimum operating temperature, fuel consumption of the motor may increase.
It can hence be advantageous to make an air inlet opening of adjustable design. To this end, the air inlet is usually coupled with an adjustment device which comprises a drive unit. With the aid of the drive unit the air inlet can be closed and be opened. When in the case of a closed air inlet the operating temperature of the motor runs up too high, the air inlet can be opened again to provide for sufficient cooling. Solutions are known that seek, in case of a failure in the adjustment device, to allow the air inlet, when closed, still to be opened.
Thus, publication DE 37 01 584 describes an air inlet that can be closed with a blind which is unwindable about an unwinding shaft. The adjustment device comprises a spring which during opening and closing of the blind is relaxed and biased to the opened position, respectively. At an unduly high operating temperature of the coolant and upon failure of the drive unit, the blind is brought to an opened position under the influence of the spring.
A drawback of the above-mentioned adjustment device is that the spring is each time tensioned upon closing of the blind. Consequently, the electric motor is of unduly heavy design. As the electric motor during tensioning of the spring is increasingly heavily loaded, the motor noise changes. This may be experienced as annoying. Also, the mechanism is relatively large, complex and costly.
An object of the invention is to provide an adjustment device of the above-mentioned type which counteracts at least one of the above-mentioned disadvantages.